This invention relates to marine drive units for boats, specifically of both the outboard type and the inboard-outboard type, and more particularly to the safety mechanisms which permit and provide their movement particularly when the drive unit encounters an underwater obstacle during movement of the boat through the water.
Heretofore in the art, the only provision for limiting potential damage experienced by outboard and inboard-outboard type drive units during operation have been variations on locking safety tilt mechanisms that permit the drive unit to tilt arcuately about their mount on the transom of a boat when the impact against the lower portions of the drive unit is sufficient to overcome the forward thrust produced by the drive unit during operation. In all cases however, the impact required to operate the safety systems of the prior art require that the drive unit itself must collide with an obstacle directly and receive the impact of that collision in order for the drive unit to be caused to tilt.
As any boat operator knows, marine drive units are expensive pieces of equipment, and it is highly disadvantageous for them to be struck at all, and often such impacts result in varying degrees of damage to the lower unit, the tower housing, the propeller, internal drive components and safety release mechanisms of these units, and even to the transoms of the boats themselves in severe impact situations, as in fast travelling boats.
Moreover, locks have to be provided to prevent tilting of the drive units when they are being used in reverse, else propeller thrust simply tilts them into non-functional positions. Also, in the case of inboard/outboard type outdrives, steep tilting of the unit when the engine is running results in serious damage to the U-joint drives and the gear drives. Internal damage is frequently consequent of tilting during an impact or when a boat owner runs his outdrive in tilted condition in shallow waters.
Illustrative of conventional safety tilt mechanisms of the prior art are U.S. Pat. Nos. 3,470,844; 3.570 443; 3,577,954; 3,648,645; 3,722,456; 3,859,952; and 3,952,687. U.S. Pat. No. 3,469,558 discloses an extremely complex, combination boat hull and motor/drive shaft pivot mount arrangement designed to protect the propeller of an inboard-powered boat from damage during an impact. U.S. Pat. Nos. 3,807,347; 3,980,039 and 4,089,290 disclose basic mounts for movement of the drive units vertically between operative and inoperative positions on a boat. Nowhere however has the industry sought to avoid actual damaging contact of the outdrive units with an obstacle in order to operate safety mechanism which will automatically remove the drive unit from the potential of injury during operation. In all instances, the operation of the drive unit protection systems are activated and operated solely by virtue of the impact of the expensive drive unit with an underwater obstacle.